I would go about it 1 of 3 ways.
1. Either this:
Why not just replace the seven Lawbreaker powers with one?
That way, it costs two refresh at most. Which is affordable.
2. I would not require the PCs to take lawbreaker... reasoning that they found magic /after/ being killers, and that as long as they don't try to time travel and just stick to killing and torture, they are being true to themselves and they believe it's ok.
3. I would model their powers based on actual powers rather than magic. For instance, a breath weapon with more ooomf for pyrokinesis etc.
Since a real evocator would need to be taught, and since the person teaching them would know about the white council, I would actually tend to lean towards option 3.
Just like the shape shifting Alphas, the powers that the team manifests could be a display of discipline, a little knowledge, and a lot of hard work.